Can DQN perform better than Double DQN?
There is no thorough proof, theoretical or experimental that Double DQN is better then vanilla DQN. There are a lot of different tasks, paper and later experiments only explore some of them. What practitioner can take out of it is that on some tasks DDQN is better. That's the essence of Deep Mind's "Rainbow" approach - drop a lot of different methods into bucket and take best results.